When playboy Roger Carlyle met the African Woman, he took a turn for the worse. Every morning he related strange recurring dreams full of Egyptian symbols and mystic beckonings. Though never before interested in Egypt's history or archaelogy, Carlyle suddenly organized an archaeological expedition to that ancient land. His friends were puzzled, and the newspaper gossip columns were fascinated. No one ever imagined that the expedition would meet such a terrible fate a few months later . . . .

Setting include New York, London, Cairo, Nairobi, and Shanghai; puzzling clues are discovered in each locale, but can the hapless investigators survive long enough to make sense of them? Background notes and a variety of play aids help keep players and investigators on their toes during dozens of discrete adventures. Horrifying schemes, deadly adversaries, and sanity-threatening events challenge the coolest investigator as the team attempts to unravel the fate of the Carlyle Expedition.

Masks of Nyarlathotep includes more than 140 pages of role-playing information.

To play every scenario in the campaign, Keepers also were required to own Terror Australis. The scenario City Beneath the Sands was cut from the original release of The Masks of Nyarlathotep to conserve space and later released in Terror Australis. City Beneath the Sands was later included in The Complete Masks of Nyarlathotep.

It should be noted that although the 2010 release is titled "Masks of Nyarlathoteop", it is actually a reprinting of "The Complete Masks of Nyarlathotep". It does include the City Beneath the Sands.